A wide variety of multimedia applications currently available on-line, e.g., from the Internet, allows users to upload and share photographs taken with a variety of multimedia apparatuses on-line, e.g., through Internet blogs. With such renewed interests in taking and sharing photographs, camera ownership has also seen a sharp rise in the recent years.
Cameras may broadly be classified as single-lens reflex (SLR) cameras, twin-lens reflex (TLR) cameras or rangefinder (RF) cameras according to the type of viewfinder used.
An SLR camera has only a single lens through which users may both view and capture the image of a subject. Light passing through the single lens is reflected by a mirror at approximately 90° angle so that users can view the subject with his or her eyes through the viewfinder. Accordingly, SLR cameras advantageously provides a user with an instant feedback through the viewfinder of whether the subject is in focus or of how clearly a scene can be viewed in the foreground in relation to the background.
A TLR cameras include separate lenses for taking photographs and for the viewfinder, and tend to be relatively expensive and medium-sized cameras.
An RF camera has an additional viewfinder for displaying an image that is similar to the image captured by the objective lens. However, since the viewfinder of the RF cameras is not optically coupled to the object lens, no change appears on the viewfinder screen even when the focus of the objective lens and/or the iris changes. RF cameras generally tend to be small cameras.
While the three camera types have each been in use to varying extents, SLR cameras have been the generally preferred choice for those prefer the viewing of the images as they would be captured by the camera. In the digital era, digital SLR (DSLR) cameras have similarly become widely popular.
A modern camera typically includes an automatic focusing (AF) detecting function, which enables automatic focus adjustment. An AF system generally measures the distance between two images formed on an AF sensor, calculates how far the object lens should be moved to make the subject in focus based on the measured distance, and moves the lens until the subject is in focus.
The focus area of a conventional SLR camera is limited to the central portion of the photographed image due to the optical asymmetry. However, a typical user desires a broader focus area as a preferred feature in a modern SLR camera.
Unfortunately, however, when the focus area is broadened, e.g., to encompass the entire image, the optical asymmetry also increases, and therefore the resulting focus of the image becomes off towards the edges of the image.
As an attempt to address this issue, a lens may be added to an SLR camera. However, there may be spatial limitations in a camera that may make addition of a lens difficult.
An SLR camera that offers a broad focus area while addressing the optical asymmetry without requiring an additional lens is thus desired.